A PUBLICATION OF THE HARVARD GROUP
VOL.3 NO. 3
IN THIS ISSUE
Income Tax 8
Flashing Prompts 19
Video Artist 10
Translating Programs . . 3
Machine Language Pro-
gramming Made Simple. 20
Classified Ads 21
Curing 16K Dumping 20
Dear Edi tor 14
ZX Printing 4
Hardware Hints 7
Marex ROM Switch. . . . . 16
Flags Register 17
News /New products 1,2
Numbers Held Inaccurately
on the ZX81 6
Program corrections and
Software Hint 5
Users ' Groups 15
Index of Advertisers
Kopak Creations 19
LJH Enterprises 11
Mindware Co 6 , 16
RKL Systems 20
S & S Co 18
Sinclair Research. .. 12 , 13
Zeta Software 7
IAN LOGAN WINS FIRST ANNUAL ROSETTA STONE
Dr. Ian Logan of Skellingthorpe , UK, a
frequent SYNTAX contributor, won the first
annual Rosetta Stone award sponsored by
Mindware Co. of Way land, MA. Given for the
best independent product-- application, soft-
ware package or peripheral-- for ZX80/ls,
future prizes will be awarded by SYNTAX
editors. Dr. Logan won $100, a US computer
magazine subscription, and a Rosetta Stone
replica for his 8K ROM disassembly.
To nominate a product for next year's
award, send the developer's name, address,
and phone number with a description. To
enter a product, also send the item plus
documentation to SYNTAX Rosetta Stone Award,
RD 2 Box 457, Harvard, MA, 01451.
TIMEX TO MARKET SR PRODUCTS IN NORTH AMERICA
Sinclair just announced a license with
Timex to manufacture and retail Sinclair
computers, peripherals and software via Timex
outlets in N. America. Expect the change
this fall. Sinclair will then stop selling
by mail and you can buy Sinclair products at
stores. We don,' t know which stores yet.
64K RAM AVAILABLE MID-MARCH
Memotech's new 64K plug- in RAM will be
available in March for $199 US. Contact
distributor Gladstone Electronics, 901
Fuhrmann Blvd, Buffalo, NY 14203, or 1736
Avenue Rd, Toronto, Ontario M5M 3Y7.
AUTHORIZED SINCLAIR REPAIR SERVICES
MicroSync Services will take over
Sinclair's repair work for ZX80s and ZX81s
(kits and assembled) and 16K RAMs . They also
offer $10 yearly maintenance contracts. Send
SASE to MicroSync Services, Customer Service
Dept, 162R Marlboro St, Keene, NH, 03431.
SYNTAX ERROR: Lawrence Souder
reported an error in his 4K Phone
Number Word Generator program
(Feb. 82). Line 110 should read
NEXT Z, not NEXT X.
Lori Olson's simultaneous equa-
tion program contained two typos:
80 FOR H=l TO 1-1
110 NEXT J
Tom Finley sent these improvements
to R.F. Fraser- Smith's 8K Digital
Clock (Nov. 81):
200 IF H<10 THEN LET D=19
201 IF H>=10 THEN LET D=18
202 IF M<10 THEN LET E=22
203 IF M>=10 THEN LET E=21
206 PRINT AT 2 1 ,D; H; " : 00"
208 PRINT AT 21,E;M;" ";M$
To run Hexadecimal Math (Dec. 81)
with an 8K ROM, make these changes
from Leo Morgan of Peabody, MA:
90 DIM (2)
180 LET N(1)=D
2 30 LET N(2)=D
240 IF C=2 THEN LET D=N(1)+N(2)
250 IF C=3 THEN LET D=N(1)-N(2)
260 IF C=4 THEN LET D=N(1)*N(2)
270 IF C=5 THEN LET D=N(1)/N(2)
3 70 FOR X=1 TO 4
500 DIM H(4)
580 PRINT CHR$ (H(4));CHR$ (H(3
));CHR$ (H(2));CHR$ (H(1));
Clifford Efaw of Morton, WA, sent
these changes to run 4K Blackjack
(Jan. 82) with 8K ROM:
370 LET X=INT (X*52)+1
670 PRINT P(Z),CHR$ (15)
I finally figured out the
computer's defensive moves for my
Awari program (Feb. 82) to improve
the play for better players. These
additions foresee the consequences
of a second move by the human,
improving the original version in
Basic Computer Games. The addi-
tions yield approximations only--
they don't add a point to the
opponent's score for passing home
on the way to a zero pile or for a
second move--but in general they'll
make the right move. The change in
line 330 avoids repeating a previ-
ous 'move. You can eliminate lines
270-290 since the Sinclair won't
invariably move pile 1 following
pile 4 and leave you to move pile 5
for 6 points. Unfortunately the
initial move is always pile 4,
which is a bit repetitious.
Change these lines :
3 30 LET Hl=-99
371 LET Q=0
372 FOR T=1 TO 6
373 IF A(T)=0 THEN GOTO 381
374 LET R=0
375 LET U=A(T)+T
376 IF U>14 THEN LET U=U- 1 4
377 IF U=7 THEN LET A(T)=0
378 IF U=7 THEN GOTO 372
379 IF A(U)=0 THEN LET R=A ( 1 4-U
) + 1
380 IF R>Q THEN LET Q=R
381 NEXT T
382 LET H2=A(14)-A(7)-Q
• 390 IF M=14 AND K=2 THEN LET H2
400 IF ABS(H1-H2)<1 THEN LET H2
Jon Passler, Beverly, MA
EDUCATIONAL SOFTWARE VENDOR
Edson Electronics now offers
educational programs for ZX80/81s
with elementary school level arith-
metic, spelling, and counting
exercises (9 learning plus 3 game
programs). Programs require 8K
R0M/2K RAM. Listings plus documen-
tation are $14.95, tapes are $12.95
(both for $24.95). Edson also has
a digital VU meter for $28.95 to
monitor cassette loading and help
eliminate loading problems. Edson
Electronics, PO Box 151211, Tampa,
FL 33684, 813/870-0282.
Remember to return your white
renewal card within two weeks of
our postmark to get a free SYNTAX
TRANSLATING PROGRAMS: ON... GO TO
Revising some programs for use
on your ZX80/81 requires total
knowledge of that computer language
and its usage. One such term that
you will stumble over is the
ON... GO TO or ON... GO SUB state-
ment. A program line might read:
90 ON X GO TO 100,10,333,2000,59
The computer compares the
value of X with the line. If X=l
then it will GO TO line 100, if X=2
then line 10, if X=3 then line 333,
etc. The same thing will happen if
the line reads :
90 ON X GO SUB 100,10,333,2000,59
Notice that if X does not
equal any number 1-5, the computer
moves to line 91. In other words,
if X equals a negative number,
zero, or a number greater than 5,
the computer skips that line.
One- revision method is to list
the numbers :
90 IF X=l THEN GOTO 100
91 IF X=2 THEN GOTO 10
92 IF X=3 THEN GOTO 333
If you use GO SUB instead of
GOTO, check for RETURN statements.
For instance, if line 92 reads IF
X=3 THEN GO SUB 333, then a line
following line 333 must have a
A second revision method is
the COMPUTED way, like 90 GO TO
X*100. If X=3, the computer goes
to line 300. Using this method,
the computer will go to any value
of X (it will even search for a
negative line number) .
A third revision method is the
DIM- ARRAY way, using a dimensioned
array containing the line numbers .
See SYNTAX (Dec. 81 p. 18) for this
type of data storage.
The computed method uses the
fewest bytes and runs at the slow-
est speed, since it must compute
each GO TO. The listed way is
somewhat faster. The array method
is quick if the DIM statement is
near the beginning of the program.
Mort Butler, BW Sabre, Houston, TX
/ ZXCHESS is the fastest, most
y versatile chess program
available for the Sinclair. With
seven levels of play, ZXCHESS
has the ability to accept and play ,
all standard chess moves in- 1
eluding castling and en passant |
This sophisticated program has a detailed «■
display of the playing board and allows you to ^
change sides and even levels of difficulty during
You can set up the board at any point in the
game to examine a special position. If you get
stymied, the program will even suggest a move,,
for you. I J
SUPER INVASION REVERSI ROAD TO RICHES
CYBORG WARS WALLBUSTERS SPACE TREK
TEN EXCITING PROGRAMS
WRITE FOR FREE CATALOG
C Please send me _
@ $24.95 each.
□ Please send me _
. Please send me a free software catalog
Please add $1.50 shipping & handling
New York residents add sales tax.
SEND CHECK OR MONEY ORDER TO:
PO Box 480, Murray Hill Station, New Mxk, NY 10156 (212) 685-2080
Foreign orders must be paid by International Money Order or
foreign draft in U.S. Dollars drawn on a New York bank.
TECHNICAL DETAILS FOR ZX PRINTING
Although Sinclair's printer is
not available in the US yet, we got
a British model and dissected it.
We suggest that when and if you get
one, you NOT dissect it--it's
surprisingly tough to reassemble.
Here's how the ZX printer talks to
the 8K ZX80/81. (The 4K ROM does
NOT support printing.) With this
info you can start interfacing dot
print mechanisms to ZX81s.
Your computer contains a 33-
byte buffer in RAM, named PR- BUFF,
starting at address 16444. In the
ROM, routines for LPRINT, LLIST and
COPY take character codes from this
buffer, transform them to dot
patterns using patterns stored in
ROM beginning at 1E00H, and send
them to the bus for the printer to
use. The ZX printer accepts this
SERIAL data and prints DOTS to form
Data to the printer consists
of instructions to draw a picture
of the characters, one 32- character
(or 256-dot) line at a time. Eight
consecutive lines of dots form one
row of characters.
Although the computer and the
printer exchange several pieces of
data, the principal data are the
request from the printer to send
the next dot and the instruction
from the computer to print the next
dot. Auxiliary signals tell the
printer how to control the motor
and inform the computer that the
printer is connected and the stylus
is on the paper. All signals pass
in and out through the Z80 accumu-
lator, or A register.
ZX printers function like a TV
picture, scanning from left to
right. A belt pulls a conductive
stylus quickly across the paper,
and where a black dot is wanted a
pulse of current is passed through
the stylus. This evaporates the
aluminum coating on the paper,
exposing the black backing. To
avoid the need to return the stylus
rapidly to the left hand edge of
the paper, two styli, equally
spaced on a moving belt, follow
each other. Thus one leaves the
paper as the other arrives in quick
succession. The belt and the paper
feed roller are both driven contin-
uously while printing, so when the
next stylus comes round the paper
has moved up to the next line.
So that the styli always stop
off the paper, the BASIC commands
slow the motor for the last two
scans before stopping-- this makes
the graphics join up if done in
several goes; put this feature in
any machine language program that
requires the printer to stop while
the computer works out the next
line. At full speed, each pen is
on the paper for about 32mS and off
it for about 16mS. Since the motor
speed can vary, an encoder disc is
used to give 256 pulses across a
92mm printing width (allowing 4mm
margins). These pulses are syn-
chronized with the stylus hitting
the paper to keep the printing
There are about 60uS between
the starts of successive pulses at
The printer is wired as a Z80
I/O port, selected by A2 being at a
low level--no other address lines
are recognized. Sinclair always
calls this port as OOFBH (251dec)
in software, but does not fully
decode the address in hardware. So
to send information to the printer
use the Z80 command: OUT(FB) ,A--
OPCODE D3 FB, assuming the data is
in register A. The data bits have
the following meanings:
D2 high means stop the motor,
low means start it.
Dl high means put the motor at slow
speed--D2 high overrides this
D7 high applies power to stylus.
On the printer side of the
interface all these lines remain in
the state they were last, until new
data is sent to the printer. At
switch on, or after pressing the
feed button, Dl and D7 are set low;
D2 stays high after feed. The
other data lines aren't used.
To fetch information from the
printer, the Z80 instruction: IN A,
(FB)- -OPCODE DB FB--will put data
into the accumulator. These bits
D6 will be read as low if the
printer is there, high if it
isn't, and is used solely to
check if printer is connected.
DO is the signal from the encoder
D7 is high when the stylus hits the
DO and D7 are both latched on the
printer side of the interface so
they remain high until the computer
writes something to the printer.
So even if you don't make use of
the information you read in, use an
output instruction with appropriate
data to reset the latches until the
next signal. These bits may be in
either state on switch on, and are
unaffected by the feed button. The
paper detect signal is also used
internally by the printer to make
sure the styli stop off the paper.
If power is applied to the stylus,
the paper signal will go high even
if the printer is between scans;
turn the stylus off before trying
to detect the paper edge.
All printing is done in FAST
mode. The COPY command prints a
full screen in 12 seconds.
All ROM code to control print-
ing appears to lie between 0802H
and 0918H, based on a quick look at
Ian Logan's ROM disassembly. A
call to 0871H (USR 2161) prints the
characters stored in the printer
buffer, then clears the buffer.
SYNTAX (02/08/13) describes a
port interface, including a schema-
tic for another address, that you
can easily modify. Simply use
address lines A0-A7, IORQ, and RD
or WR to select address, port, and
direction. Use D0-D7 to carry data
to and from the accumulator. Use
74LS75s to latch the data in and
out, and use LS-series gates else-
where when they connect to the
You can use Ian Logan's anno-
tated ROM disassembly to examine
the Sinclair software that executes
the LPRINT, LLIST, and COPY func-
tions. You can move the COPY- BUFF
and output routines to RAM using a
program suggested in Sinclair's
printer manual. First POKE 16389,
124 and NEW to set aside memory for
the machine language routine.
Next, use the following code to
move the ROM routine to RAM.
5 FOR 1=0 TO 112
6 POKE 31744+1, PEEK (2161+1)
7 NEXT I
9 POKE 31857,201
Call this routine using USR 31744.
This routine will now read
character codes, which you must
POKE into PR- BUFF, and translate
them into dot codes using the
patterns in ROM. The buffer is NOT
cleared by this routine.
If you want to store different
patterns, POKE them into the 256
bytes starting at 32256 (the space
is already set aside) and POKE
31800,63 (to restore the ROM as dot
source POKE 31800,15).
Each successive byte stores
the 8 dots for a row of printout of
one character. The ninth byte thus
contains the first row of the
second character in the set. By
defining bit patterns here you can
define a new character set. Speci-
fy all 8 bytes for each character.
My son finished off a recent
program for me thusly:
9950 SAVE "Name of. Program"
9960 GOTO (First line of Program)
To SAVE this on tape, I just type
GOTO 9950 instead of the more time-
consuming SAVE "Name of Program".
Herb Sturges , Orinda, CA
am -'-... ••'^-'-■ x -\-
... a powerful combination at a bargain price!
MINDWARE introduces COMPUTACALC.
a low priced software package tor
the ZX01. COMPUTACALC is an
electronic worksheet with an
almost unlimited range
o. applications. CONSIDER:
A versatile tool for $39.93
Requires 16K RAMPAK
mindware has a catalog of
software, hardware and books
for the 2X81.
"TT?fS ., MINDWARE CO.
.'•4. *-a M* Z"'t P'OOuiis "*■*' supp/*'"e«f mature \ compute?
NUMBERS HELD INEXACTLY ON THE ZX8]
This is the first of several
articles by Dr. Frank O'Hara on
numerical errors in the ZX81's 8K
ROM floating point. --AZ
All floating-point systems
require certain techniques of
rounding, general approximation and
slightly over- or under-stating
numbers to make the arithmetic
work. The problem is particularly
acute in the ZX81 because 1) all
numbers, even integers, are held in
floating-point form; 2) of the
almost total lack of instruction in
floating-point techniques in the
manual or the literature; and 3)
the limitation of the ROM to 8K and
the premium on every byte.
In doing arithmetic on the
ZX81, it helps to know just which
numbers are held exactly in its
BASIC and which are not. This
small program shows you exactly how
any number is held on the ZX81:
10 INPUT X
20 LET V=PEEK 16400 +256*PEEK
30 FOR I=V+1 TO V+5
40 PRINT PEEK I;"
50 NEXT I
70 GOTO 10
INTEGER POWERS OF 2: To use this
program, RUN it and first enter
to satisfy yourself that is held
as five zeros as the manual says.
Then try some small integer powers
of 2, like 1 (or 2°), 2, 4, 8.
You'll get 129 0; 130
0; 131 0; and 132 0.
Before explaining this, let me give
you a program to generate all
integer powers of 2 from 1 to 126.
First delete Tine 10 from Program 1
and replace 3 Lne 70 with 70 RETURN.
Then add these lines to give:
(lines 30- 7T .rom Program 1)
100 LET X=l
120 FOR J=l TO 126
130 PRINT J;" ";
140 LET X=2*X
150 GOSUB 30
160 NEXT J
Finally, make line 20 be line 110
and delete the old line 20. To
run, press GOTO 100 then NEWLINE
(NL) or ENTER. The first 22 powers
of 2 wr*H appear, each in the form
(129 plus n) for the nth
power. To see the other 5 screen-
fuls , continue in FAST at about 7
seconds per screenful. You should
then be convinced the manual has
got it right on this point. After
seeing the 126th power (255
0), try PRINT 2*X. You'll get
report 6/0 for arithmetic overflow.
The ZX81 cannot hold. 2 to the 127.
To see the negative powers of
2, replace line 140 by LET X=X/2
and change 126 to 140 in line 120.
RUN 100 and you get the powers from
2" 1 (128 0) to 2-128 (10
0). From -129 to -140 the powers
should all be held as zero (0000
0) , but here we meet our first
quirk of the ROM. On division by
2, 2 -128 becomes 2 -129 and is
promptly rounded up to 2~^- 2 ° again!
So our innocuous little program has
got us stuck here. Try LET X=X/4,
then GOTO 30 (NOT RUN 30) and you
will get and of course
report 7/70 (RETURN with no GOSUB) .
If you have the patience to run the
program again with 128 in line 120,
you can use this same method to get
a zero result for 2"130_ If you
want a zero result for 2~129 you
have to fall back on the the
otherwise less accurate type of
expression LET X=2**-129.
So we have a simple way of
generating the exact representation
of integral powers of 2 on the ZX81
(except for 2" 129), We se e that,
as we expect from the manual, 2 n is
given by (129 plus n) where
n equals -128 to 126 inclusive.
Now compare these exact
results with the expression 2**N.
To do this , produce Program 3 from
Program 2 : Make sure that line 120
contains 126 and change line 140 to
LET X=2**J. RUN 100 and note the
19 inaccuracies at the powers 13,
26, 27, 31, 52-54, 61, 62, 104-108
and 121-125. Running the negative
powers reveals similar inaccuracies
at corresponding negative powers.
Note in particular that PRINT
2**13-8192 gives .000022888184.
That extra 6 in the last byte is
3/2 1 ?, about .00002. The inaccur-
acy arises because the ROM evalu-
ates 2**13 by approximate methods
as EXP (13*LN2). Of course,
8192.00002 may be accurate enough
for most purposes, but it may help
you to know that it is not com-
pletely accurate and you can always
get it exactly if you need it by
2*2**12. The same holds for any
other inaccurately held powers . For
example, the important number 2^1
is given exactly by 2*2**30 or by
2**32/2. So Euler's famous prime
can be got quickly by 2**32/2-1.
Next month: Positive integral
powers of 10.
Frank O'Hara, Surbiton, Surrey, UK
NEW ZX81 IK PROGRAMS by ZETA Software
on cassette tape with listings
ZETAPAK #1; WAR GAMES
Bomb Run, Sub Hunter, Barrage,
Fighter Pilot*, Torpedo Alley*,
& Dragon's Teeth*(tank battle)
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Greenville, SC 29608-3522
Or write for catalog of 50+ titles.
In Europe, send Inquiries only and U$l
bill or DM2 stamp to: DELTASOFT ZP2,
0sterfeldstr.79d,D-2000 Hamburg 54.GER
Overheating: EZUG (Educational
Users' Group) newsletter F.-nrts a
reader's solution to over ing.
He filed off the raised ZX81 name,
then put a solid block of steel
about the size of a pack of cigar-
ettes on top of the case. A simi-
lar copper block copper keeps the
transformer cool. Reprinted by
permission, EZUG Newsletter, Jan/
Feb 82, p. 16, Highgate School,
Balsall Heath Road, Birmingham B12
Memory Loss: One of SYNTAX'S
machines displayed memory loss ,
partial characters and other
strange symptoms. We tracked it to
defective solder joints on the
component side of the board at the
regulator IC. Under a magnifier,
defective joints look like conical
pits around one or more of the 7805
pins. Touching up the solder cured
all the symptoms.
It's that time of year again
and I hope that TAX will reduce
some of the nuisance of tax return
preparation, if not the pain in the
pocket. It is designed to aid in
year-end form preparation and also
to allow periodic monitoring of tax
liability during the year. You may
be able to reduce the amount with-
held from your salary or the amount
of your quarterly payments if self-
employed. Personally, I'd rather
have the money during the year than
have the IRS hold it for me.
Lines 100-152 provide the main
menu of functions with line 170
serving as an error trap for acci-
dental entries. You can quickly
see the program's various capabil-
ities. Tax calculation includes
all arithmetic and transferring
totals to appropriate lines.
The PAUSE subroutine at lines
6000-6030 allow you to view various
displays as long as desired before
proceeding. The form selection
subroutine is at lines 7000-7214.
Although this listing includes only
Form 1040 and Schedule A, you can
add any additional forms using the
same principles illustrated. The
particular variables allow this
flexibility. Z is the offset in
line numbers for each form with
allows all line numbers and des-
criptions to be stored in a single
sequential array but allows you to
enter the line numbers on the IRS
form. P is the number of "pages"
used to display the given form.
Each value of J is the starting
line for each display page; each
value of K is the ending line.
This allows overlap of displays as
Lines 1000-1120 provide the
data entry function and begin with
form selection through GOSUB 7000.
You are then prompted for line
number and amount. The amount is
added to the previous total for
this line and the new total
displayed. This allows periodic
updating during the year and
revisions during year-end form
preparation. Make negative correc-
tions by entering negative numbers .
Lines 2000-2248 perform all
arithmetic for lines that require
it. Schedule A (lines 2200-2248)
must be done first so that Form
1040 (lines 2100-2182) will have
that information. Lines 2120-2122
require you to refer to the tax
tables for the tax on the amount in
Form 1040 line 34. Lines 2124-2126
request any additional taxes. The
"bottom line" is displayed by lines
2174-2178. In the calculation of
Schedule A, the total deduction is
displayed by 2242.
Lines 3000-3080 allow you to
view all line items on the form
selected. GOSUB 7000 illustrates
its usefulness here by allowing a
short subroutine to serve for all
present and future forms . Line
numbers, descriptions and amounts
are presented. Changing the line
number I to 1$ makes for a more
Lines 4000-4060 record the
program and all variables, includ-
ing line descriptions and amounts.
This also makes the program self-
starting upon LOADing and elimin-
ates the danger of erasing every-
thing with a RUN instead of a GOTO.
Lines 5000-5030 erase all line
amounts to let you keep the line
descriptions intact when starting a
new tax year.
Lines 9000-9050 are for
initializing the program. The REM
statements indicate direct commands
that should be entered when the
program is being initialized. Line
descriptions are typed in by first
commanding GOTO 9020. The prompt
provides a guide to the maximum
length of the description (18
spaces) by printing 16 *s after the
line number. The direct command
LET J=l allows later addition of
forms and line descriptions.
Setting J to the new line number
saves previous entries. The number
10 7 is the total lines in Form 1040
and Schedule A. If you add more
forms to the program, you must
increase 107 wherever it occurs.
After initializing TAX, enter
GOTO 100 to get to the main menu
and either begin using it or record
it for later use.
Lane Lester, Lynchburg, VA
Enter all data that cannot be
computed on Form 1040 or Schedule
A. Run CALCULATE TAX routine on
Schedule A first; totals are auto-
matically transferred to Form 1040.
For lines on Form 1040 with sub-
lines a, b, c and d, enter each
sub- item to the main line number.
The screen shows the latest entry
and the total. You can only go
forward through the form; enter
zeros until the main menu comes up
to go back.--K0
(Mar. 82 listings are printed on a
Sinclair ZX printer. Comments?)
'i^PRINT RT 3.. Sj ; "INCOME TRX RE
^RINT RT 6, 4.; "PRESS DESIRED
JRT 8,6; "1. ENTER DRTR
rt :9,,e;< u s« crlgulrte
fiT,,10,e;"3. REUIEU DR
I^R#xiMT, fVT X\s6;"4. .RECORD DR
fcjpftlNT 1 " RT 12 , 6.: "5 . ERRSE RLL
rSfiBSi** 1 - 1 ' ''
70 ^K$£"^ K OR^K*>" 5 « THEN GO
ISO GOSUB_ URL K»» l»—
iSS I _
1810 PRINT RT 6..S.:"l_INE NUMBER"
1820 INPUT Y
1030 PRINT RT s..ae:Y
104.0 LET X=Y+Z
1OS0 PRINT RT S..S.; "RMOUNT *"
1060 INPUT R
1070 PRINT RT S,16;R
1080 LET L (X) =L(X) +R
1090 PRINT RT 10,8,"TOTRL *";L(
1100 GOSUB 6000
1120 GOTO 100
1999 REM .
2000 GOSUB 7Q<_ _
£020 GOSUB ORL k** 188+2080
2099 rem aEHMBBB
2100 LET L (21) =0
2102 FOR 1=7 TO 2©
2104 LET L (21) =L <21> <-L *I*
. .. $ .
LET L (30) =0
FOR 1=22 TO 29
LET L.(30) =L (30.* +L CI J
=L (21) -L (30)
=L (31) -L (32) -L (33.*
21,0; "ENTER TRX FO
8; "ENTER RDDXTI *
(37) =L (35) +L (36)
1=38 TO 45
L (46) =L (46) +L CI)
LET L (47) =L (37) -L C4-6)
LET L (54) =0
FOR 1=47 TO 53
LET L (54) =L (54-) -fL CI)
LET L (62) =0
FOR 1=55 TO 61
LET L (62) =L (62) +L CI)
LET X=L (62) -LCS4-.)
IF X<0 THEN GOTO 2166
LET L (63) =X
LET L C64-) =L (S3* -L C6S)
LET L (63) =0 , -
L (64) =0
L (66) =X*<-1 ,
1=63 TO 86 |
RT 1-53,0^1;" ";C$CIJ
LET L(70) =L (63) -L (69)
IF L(69)>L(68) THEN LET
LET L (73) =L (70) +L (71 J *L (72)
LET L (74.) =.03*L C3i>
LET L (75) =L(73) -LC74-)
IF L(74)>L(73) THEN LET L (7
LET.^L (76) =L (67) +L (75)
LET L (82) =L (77.) +L (78) +L (79)
+L (88) 4L (31)
2216 LET L (86)
2218 LET L(90)
2220 LET L (95)
=L (83) +I_ (34) +L (85)
=L (87) +L (88) +L (89.*
=L (91) +L (92) +L (93.)
=L (99) +L C100) +L (1
01) +L (102) +L (103) +L (104)
2238 LET L ( 107) =L (185) -L C 106)
2240 IF L (106) >L (105) THEN LET L
( 107) =0
2242 PRINT RT 15,0; "4-1 ";C*(107>
.: " *";L(107)
2244 GOSUB 6000
3008 GOSUB 7000
301© FOR N=l TO P
3820 FOR I=J (N) TO K (N)
3025 LET I*=STRS I
PRINT 1$; "
PR INT OT ©
10.. 3.: "PRESS RNY KE
Y UHEN READY"
4030 PRUSE 40000
4050 SRUE "TflB"
4868 GOTO 100
5005 FOR 1=1 TO 107
5010 LET L(I) =0
5020 NEXT I
5030 PRINT RT 10,7,"RLL ENTRIES
5999 REM SHi
PRINT RT 21.. 3; "PRESS RNY KE
PRINT RT 6, 7; "PRESS DESIRED
RT 8,9; "1. FORM 1040"
RT 9,9.; "2. SCHEDULE R
7082 PRUSE 4-0000
7004. LET K*=INKEY$
7088 IF K*<"1" OR K$>'
URL K**100 4-7000
d (1) *7
U (2) =21
J (4.) =4-7
K (1) =21
K t>3) =54
LET K.C4-1 =66
LET UC1) =1
LET UC2) =21
LET K (1J =20
LET K (2) =4-1
I=J TO 107
RT 21,0.; I*,
0,11; "SCHEDULE R"
904-0 INPUT C*(I)
9850 NEXT I
VIDEO ARTIST- -8K/2K
This program shows the ZX81's
ability to draw pictures under
BASIC control. Run the program and
enter the title of your work. Hit
NEWLINE or ENTER, and you get a
flashing cursor in the center of
the screen. This is the editing
cursor. Control the direction of
this cursor in real-time with keys
5-8. The cursor moves in the
direction of the arrows on the
keys. In this mode you can move
anywhere on the screen.
To start drawing, press 1.
This puts the computer in plot
mode. Again, you have real-time
directional control by pressing
keys 5-8. To erase, go back to
edit mode (hit 0) and move the
cursor over the line to erase.
When you finish a masterpiece,
you can save it on tape. Turn on
your recorder and press S. It
saves under the title you gave it.
You can exit just about any
time by pressing BREAK. This
program should run in 2K RAM for
those of you who have modified your
ZX81's or added a 16K RAM pack.
Lance Ward, Lansing, MI
PRINT "ENTER TITLE.
IF INKEY$ = "'8"
IF INKEY$ = "1""
LET Y=Y +
THEN GOTO 100
LET Y=Y +
ANOTHER $100 MISUNDERSTANDING
I just finished rebuilding my
ZX81 kit. If Sinclair had sent
complete instructions with my kit
(delivered in early Jan. 82) I would
not have needed to reopen the case,
desolder and remove two components,
and add seven new ones. I can't
believe that Sinclair singled me
out to receive a kit with incom-
plete instructions, so what follows
may help others whose ZX81s won't
work and wonder why they have two
resistors, two capacitors, two
little red coils and an oddly
shaped metal strip left over after
finishing the assembly per
Instructions with my kit
called for only 12 capacitors (Cl-
C12) to be installed on the board.
They didn't mention two red-wire
induction coils. They offered no
special instructions for installing
R27 and R29 . And they didn't even
mention a grounding strip, let
alone describe how to install- one.
If the instructions you got are
similarly lacking, take note.
Sinclair advises (after I
wrote) that you install R27 and R29
vertically. You should find two
pairs of resistors of the correct
values (R27=1K, R29=1M) . Use the
pair that are preformed for verti-
You will also find two surplus
47nF capacitors (marked 473 Z) when
you finish the assembly per the
instructions. These are C13 and
C14. It's easy to spot the board
location for C13, but the callout
for C14 is hidden under the 9V
jack. The C14 location is between
the end of the jack and the edge of
It is easy to spot the
locations for inductors II and 12,
just above the regulator. Plug the
red-wire coils into these locations
(II and 12 bring the 9V supply to
the regulator, without them the
board is stone-cold dead). Solder
all these components to the board.
• Standard Computer Keyboard
• Type programs in half the time
• Minimize errors
• Wired keyboard hooks up in minutes
Plans for keyboard conversion with reverse video
Keyboard with complete parts and plans NOW 155.00
Wired keyboard, complete with plans NOW 175.00
Add $5.00 mailing charge tor continental U.S.
Other locations write for details.
Mail for information:
P.O. Box 6305, Orange, CA 92667
or call 714/547-8717
Finally, install the left-over
weird- looking metal strip so that
its long bent-up end passes between
the heat sink and the edge of the
board, with that end in position to
contact the top of the case once
the board is screwed down. Solder
the other end of the strip to the
arrow-shaped area just below the
slot in the board. Then solder the
other portion of the strip with a
single small hole in it to the
rectangular area provided adjacent
to the regulator.
My 8K/1K ZX81 ran satisfactor-
ily with horizontal rather than
vertical resistors, without the two
additional capacitors, and without
the grounding strip. It runs even
better now with the changes and
added components. The TV display
is clearer and more steady and
seemingly, keyboard entry is faster
Bob Nadler, Englewood, NJ
the Sinclair ZX81
If you're ever going to buy
a personal computer, now is the
time to do it.
The new Sinclair ZX81 is the
most powerful, yet easy-to-use
computer ever offered for anywhere
near-the price: only $149.95* completely
Don't let the price fool you. The
ZX81 has just about everything you
could ask for in a personal computer.
In personal computers
The ZX81 is a major advance over
the original Sinclair ZX80-the world's
largest selling personal computer and
the first for under $200.
In fact, the ZX81's new 8K Extended
BASIC offers features found only on com-
puters costing two or three times as much.
Just look at what you get:
■ Continuous display, including moving
■ Multi-dimensional string and numerical
"Plus shipping and handling. Price includes connectors
for TV and cassette, AC adaptor, and FREE manual
■ Mathematical and scientific functions
accurate to 8 decimal places
■ Unique one-touch entry of key words
like PRINT, RUN and LIST
■ Automatic syntax error detection and
■ Randomize function useful for both
games and serious applications
■ Built-in interface for ZX Printer
■ 1K of memory expandable to 16K
The ZX81 is also very convenient
to use. It hooks up to any television set
to produce a clear 32-column by 24-line
display. And you can use a regular
cassette recorder to store and recall
programs by name.
If you already own a ZX80
The 8K Extended BASIC
chip used in the ZX81 is available
as a plug-in replacement for your
ZX80 for only $39.95, plus shipping
and handling— complete with new key-
board overlay and the ZX81 manual.
So in just a few minutes, with no
special skills or tools required, you can
upgrade your ZX80 to have all the
powerful features of the ZX81. (You'll
have everything except continuous dis-
play, but you can still use the PAUSE
and SCROLL commands to get moving
With the 8K BASIC chip, your
ZX80 will also be equipped to use the
ZX Printer and Sinclair software.
Order at no risk"
We'll give you 10 days to try out
the ZX81. If you're not completely satis-
fied, just return it to Sinclair Research
and we'll give you a full refund.
And if you have a problem with
your ZX81, send it to Sinclair Research
within 90 days and we'll repair or replace
it at no charge.
"Does not apply to ZX8I kits
NEW SOFTWARE:Sinclair has
published pre-recorded pro-
grams on cassettes for your
ZX81, or ZX80 with 8K BASIC.
We're constantly coming out
with new programs, so we'll
send you our latest software
catalog with your computer.
ZX PRINTER: The Sinclair ZX 16K MEMORY MODULE:
Printer will work with your ZX81, Like any powerful, full fledged
or ZX80 with 8K BASIC. It will
be available in the near future
and will cost less than $100.
computer, the ZX81 is expand-
able. Sinclair's 16K memory
module plugs right onto the
back of your ZX81 (or ZX80.
with or without 8K BASIC).
Cost is $99.95, plus shipping
ZX81 MANUAL: The ZX81
comes with a comprehensive
164-page programming guide
and operating manual de-
signed for both beginners and
experienced computer users.
A S10.95 value, it's yours free
with the ZX81.
PARTIAL INDEX, VOL. 1 AND 2
Analyzing the Problem. . 02/07/15
Computer No. Systems .. .02/02/10
Dimensioned Arrays 02/07/14
Error Codes /Debugging. .02/04/11
FOR-NEXT Loops 01/01/07
In and Out of ML 02/08/05
Loading ML Programs 02/08/11
Machine Compatibility . .02/01/10
PEEK, POKE, & CHR$ 02/06/14
Printing on 8K ROM 02/09/08
READ, DATA, RESTORE 02/12/18
Reading MC Assembly 02/09/12
REM Revisited 02/11/18
REM Statements 02/01/10
ROM/RAM Addresses 02/05/15
ROM v. RAM 02/02/11
The BASIC Handbook 02/12/09
Crash Course in
Problem- Solving Principles
for Programmers 02/09/14
The ZX80 Companion 02/07/10
The ZX81 Companion 02/11/14
All-Purpose Beeper 02/06/04
Build Additional RAM. . .02/03/02
Input Port 02/08/13
Interface to World 02/01/07
(memory -mapped output)
Telephone Dialer 02/02/05
Using Extra Keys on
Big Keyboard 02/03/07
Wiring Big Keyboard 01/02/10
Big Keyboards 02/08/04
Universal Memory Board. 02/12/08
Machine Language Programs
4K Logical AND & OR
for 8K ROM 02/07/12
MC Print Routine--8K. . .02/09/12
Syntactic Sum--8K 02/06/13
Problems and Solutions
CPU overheating 02/11/12
Disappearing character .02/10/09
Escape endless program. 02/02/12
4K Programs in 8K 02/06/02
16K RAM hum 02/07/09
Tiny keyboard 02/06/11
Programs --8K ROM
Digital Clock 02/11/15
Convergence Pattern. .. .02/12/09
Happy Holidays 02/12/17
Lights of the City 02/01/12
Slalom Course. . . .' 02/12/17
Super Monzxer 02/11/03
Brownian Motion 02/12/02
Sine Waves 02/11/02
Check Book 02/07/07
Job Review 02/12/06
Loan Amortization 02/07/06
changes for IK 02/08/03
Gas Hogs 02/09/14
Print Routine (ML) 02/09/12
Roundoff Routine 02/10/15
Sort Routine 02/10/15
Syntactic Sum 02/06/13
Tips and Hints
Bar code input 02/09/06
Bytes available--4&8K. .02/06/13
Bytes Remaining--8K 02/12/05
Debugging programs 02/10/15
Find clean tape--8K 02/11/13
Loading Technique- -8K. . 02/12/08
Memory check 02/04/06
Save bytes 02/04/06
SAVE data in arrays 01/01/05
SAVE/LOAD faster 01/02/11
Unlis table programs
Adding 48K RAM 02/11/12
Circuit to Reduce
Direct Video 02/09/06
Hardware Hints 02/11/03
Hardware Notes 02/04/04
Installing 8K ROM, 16K
RAM on MicroAces 02/04/02
Make-do connectors 01/02/03
Reverse video 01/02/09
Soldering Hints 02/08/04
ZX80 bus pinout 01/02/12
ZX80 ports Used in 8K. . 02/08/16
ZX81 2K Upgrade 02/11/07
8K ROM Features 02/05/09
8K ROM Monitor
8K ROM Potpourri 02/11/07
Improved 8K ROM 02/12/04
Intro to Machine
Logical Functions 02/07/11
and Division 02/06/05
Random Functions in 4K
& 8K 02/09/09
Translating from Other
BASICS--VAL & LEN 02/09/05
Writing Game Programs .. 02/07/03
Do you know--
o whether the Crash Course in Microcomputers will help
you? (SYNTAX 02/10/12)
o Why NOT to get Problem Solving Principles for BASIC
Programmers, but buy the "plain vanilla" Problem
Solving Principles for Programmers instead?
o What two simple components you can add to a cable to
dramatically improve SAVE and LOAD operations with
ordinary cassette recorders? (SYNTAX 02/09/11)
o How to make directions appear on the screen when you
LOAD from tape? (SYNTAX 02/12/08)
o What BASIC handbook describes Sinclair's unique BASIC
words? (SYNTAX 02/12/09)
o How to make your ZX81 keep real time? (SYNTAX 2/11/15)
o How to easily connect a bigger keyboard to your ZX81?
(SYNTAX 01/02/10, 02/03/07)
Subscribers get this kind of helpful, time-saving information
every month. SYNTAX provides a continuing service--month
after month, concise, explicit, frustration-preventing
articles and programs come to you automatically.
SYNTAX ZX80 is a monthly newsletter exclusively
for ZX80 and Micro Ace owners. We bring you
news, reviews and applications for your computer,
plus technical notes for circuit-builders. SYNTAX
also provides a forum for thousands of users to
share advice and problems about programs and
vendors. We bring you timely updates about new
hardware, software and books. And we cover all the
Sinclair-Micro Ace computers, including the new ZX81.
At SYNTAX we emphasize practicality. You can
apply our suggestions even if you aren't sure at first
why they work, because we give you complete instruc-
tions. Text is clear and easy to understand. SYNTAX
readers already know about:
• An automatic phone-dialer they can put to-
gether in a few hours
• Syntactic Sums™ to check input for errors
• Programs to explore computer memory
• How to build external additional RAM
• How to add an 8212 I/O chip to control
external devices from their computers
And SYNTAX readers like what they get every
month. Subscribers know they can depend on us.
After receiving only three issues of
SYNTAX ZX80, I find that I anxiously
await the next issue . . . keep up the
Congratulations on the brass-tacks, down-
to-earth approach of your newsletter. I'll
be looking forward to future issues.
Many readers get their first issue and immediately
order the back issues — more proof that they like
what they see.
You can see what's special about our publication.
We work hard to bring you a quality newsletter. We
strive to print useful programsof above-average
accuracy. As any computer magazine editor can tell
you, program listing accuracy is tough to achieve,
but we boost our average with every issue. We test
each program to make sure it works, it fits in the
designated RAM, and it runs when you follow the
directions. We print program listings in screen-image
format to make it easier for you (it's sure not easier
for us!) to enter programs accurately. We invented
Syntactic Sum™ as an additional aid for you in
getting error-free programs. With your subscription
you also get access to thousands of other readers,
and our staff experts are available by phone to
answer your questions or help you solve problems
with your machine.
SYNTAX readers get every month:
• Latest news of Z80 hardware and software
• Programs to organize information, calculate,
entertain, or instruct
• Do-it-yourself additions
• Clear explanations for beginners
To share the benefits of SYNTAX ZX80, just
indicate your choices on the order coupon and return
it with your choice of payment in U.S. funds.
(Please note that additional postage is required for
delivery outside North America.)
We are so sure you'll find SYNTAX useful that we
promise to refund your entire subscription fee if you
aren't satisfied. An unconditional guarantee — you
Join the others who stretch the ZX81s to their
utmost. Act now — as soon as we receiveyour
coupon with payment, your first issue will be on its
way. For faster service, phone your credit card order
to 617/456-3661. Don't miss SYNTAX!
RD 2 BOX 457
HARVARD, MA 01451
Telephone orders call
PLEASE PLACE IN ENVELOPE AND RETURN TO US
YES! Please send me 0^6 issues for $17 □ 12 issues for $29
(Add $7.50 for postage
ouiside North America
(Add $15 for postage
outside North America)
D My check is enclosed
Make checks payable to:
SYNTAX ZX80 INC.
□ Please charge my □ MasterCard
D Diner's Club □ American Express
□ VISA □ Carte Blanche account
. bank number (MC only) .
I own a □ Sinclair ZX80
□ Sinclair ZX81
□ MicroAce computer.
HOW TO MAKE AND USE AN 8K
SYNTACTIC SUM TAPE (ZX80, ZX81)
First, create the utility
tape. Key in program 2.
1 DIM P(31)
2 FOR L=l TO 31
3 INPUT P(L)
4 NEXT L
6 LET M=1024
7 FOR L=M+16352 TO M+16382
8 POKE L,P(L-M- 16351)
9 NEXT L
RUN the program and key in
the numbers from this decimal
delete lines 1-5. SAVE the rest
of the program to tape.
If you use more than IK of
RAM, use the table to alter these
instructions and Program 2.
Always POKE 16388,224 first,
regardless of mernory size.
12 64 221
32 8 125
193 201 78
When you have typed in the
final number, error 9/5 appears.
Get back to the listing (LIST) and
To use Syntactic Sum with the
8K ROM and IK RAM, do these steps:
o POKE 16388,224 and POKE 16389,67
o Type NEW (NL)
o LOAD the 8K version of program 2
o Type GOTO 6 (NL)
o LOAD or key in the BASIC program
to be summed.
o Type SHIFT F (NL) to put machine-
in FAST mode.
o PRINT USR(17376)
Syntactic Sum™ Syntax ZX80 Inc.
and The Harvard Group .
Syntax ZX80, Inc. hereby grants everyone the right to use the Syntactic Sum
program, to generate Syntactic Sums™, and to publish them with programs.
Republishing this program is strictly prohibited without our written consent.
IF YOU CAN READ THIS,
IT'S NOT WORKING FOR YOU!
Fill out the coupon on the reverse and mail it to SYNTAX now.
the ZX81 kit
If you really want to
save money, and you enjoy
building electronic kits, you
can order the ZX81 in kit form
for the incredible price of just
$99.95* It's the same, full-featured
computer, only you put it together
yourself. We'll send complete, easy-
to-follow instructions on how you can
assemble your ZX81 in just a few hours.
All you have to supply is the soldering
How to order
Sinclair Research is the world's larg-
est manufacturer of personal computers.
The ZX81 represents the latest
technology in microelectronics, and it
picks up right where the ZX80 left off.
Thousands are selling every week.
We urge you to place your order
for the new ZX81 today. The sooner you
order, the sooner you can start enjoying
your own computer.
To order, simply call our toll free
number, and use your MasterCard or VISA.
To order by mail, please use the
ooupon. And send your check or money
order. We regret that we cannot accept
purchase orders or C.O.DIs.
CALL 800-543-3000. Ask for op-
erator #509. In Ohio call 800-582-1364.
In Canada call 513-729-4300. Ask for
operator #509. Phones open 24 hours
a day, 7 days a week. Have your Master-
Card or VISA ready.
These numbers are for orders
only. For information, you must write to
Sinclair Research Ltd., 2 Sinclair Plaza,
Nashua, NH 03061.
AD CODE \iJ3SX
PRICEt QTY. AMOUNT
8K BASIC chip (for ZX80)
Memory Module (for ZX81 or ZX80)
Shipping and Handling
MAIL TO: Sinclair Research Ltd., One Sinclair Plaza, Nashua, NH 03061
t U.S. Dollars
Here's a better way to stop
the listing and editing of an 8K
program. Make the first line of
your program 1 REM X. After typing
in your program, enter with no line
number POKE 16514,118 and POKE
16509,40. This will stop the list-
ing. When you try EDIT or LIST, it
gives you A241 REM no matter where
the program cursor is .
To get out of this mode, POKE
16509,0 and POKE 16514,61.
Andrew Lederman, Pitts ford, NY
In the Feb. 82 issue, George
Luhrs asked for a linear regression
program. We have one for 8K ROM/
IK RAM or more for $2.50. It puts
the best line through x,y data
points. Ask about our business
Linear Programming system.
If you're strung for bytes,
use LET A=0 and LET A=A+1 instead
of DIM A(l) and LET A(1)=A(1)+1 for
the sum-to-memory and counter
method I described in Feb. 82.
Paul Ezra, Ezra Group II, Box 5222,
San Diego, CA, 92105, 714/584-8291
In spite of Gary Vincent's
authoritarian tone in his Feb. 82
letter about painting heat sinks, I
believe he is incorrect.
Copies of applicable sections
of the Motorola and National Volt-
age Regulator Handbooks are
enclosed to document the positive
effects of painting aluminum heat
sinks black. The effect of
increased emissivity varies with
the heat sink's parameters but
black paint always helps!
Chuck Hut ton, Atlanta, GA
Chuck included tables from the
Handbooks showing emissivity values
for various surfaces . Painted or
varnished surfaces have higher
emissivities than polished or
oxidized surfaces . --AZ
I'd like to hear from anyone
interested in putting FORTH on the
ZX80/81 or in defining a "standard"
mapping between the ASCII and ZX81
Rich Holmes, 1303 E. Wilson #204,
Batavia, IL, 60510
I bought an 8K ROM and 16K RAM
module for my ZX80. Here are some
problems I found and my solutions :
1. The ZX81 keyboard overlay
won't lay flat and bows up in the
center when attached. Apply double
sticky tape and press it onto the
existing keyboard. It lays flat
and keyboard sensitivity is
2. The 16K RAM fits loosely, as
it's only attached by the edge
connector. If it comes loose with
power on, the RAM may be damaged.
Fit a 2"x5" piece of thin PC board
material between the RAM foot, pads,
through the edge connector slot in
the ZX80 case (I whittled mine out
a little with a pen knife) and
under the ZX80 PC board. Attach it
to the RAM and to the bottom half
of the ZX80 case with short, self-
tapping screws. Reconnect the
internal gournd spring (supplies
ground from the PC board to the
lower case coating) elsewhere.
3. The 16K RAM internal ribbon
connector leads were not clipped
during assembly at the factory. So
the leads intermittently contact
the conductive coating inside the
case. As the coating has ground
applied, the consequences are
disastrous. Clip the leads.
Larry Lockwood, Yorba Linda, CA
Is anyone selling the MicroAce
Flicker-Free kit for upgraded ZX80s
and MicroAces stateside?
I got two surplus keyboards
from John J. Meshna Inc. A fantas-
tic buy for $20 each. On my 4K/16K
system I mounted the computer (out
of its case) , 16K RAM and power
supply in the keyboard. I removed
the cassette ports and remounted
them at the back of the keyboard
housing. I used the keyboard's 4
red keycaps for cursor functions ,
10 black keycaps for numerics , and
the remaining keys for standard
alpha functions and separate tokens
(such as TO, THEN, AND). I used
the circuitry mentioned in SYNTAX
(Vol.1 No. 2) for the use of the
extra keys without holding the
SHIFT down. This keyboard was
fairly easy to wire following the
instructions in SYNTAX and
On my second system I wired
the new keyboard to an externally
accessable plug. I tapped off
necessary connections on the ZX80
(8K/16K) and mounted its plug at
the top of the case where my modu-
lator used to be (I removed the
modulator after I ran direct video
out) . This way I have portability
or big keyboard features depending
on where I'm computing.
Key caps on both keyboards
were made from photocopied origin-
als. Elmers glue holds them down.
Spread a little extra on the tops
to protect them from wear (it dries
The keyboard also has a myriad
of other helpful hardware such as a
speaker with volume control, four
switches (I used one for power and
one for video select) and a number
of small lights. All in all, a
very worthwhile investment.
Russ Gagnon, Oscoda, MI
I don't know of anyone in the US
selling the MicroAce board now.
For info about Meshna's keyboard
(#SPL-19), contact Doug Meshna, PO
Box 62, E. Lynn, MA, 01904, 617/
Jan. 82 p. 9 "More Hardware
Hints" contains a number of useful
hints, but you might find Cramolin
better for cleaning and preserving
metal-metal contacts . Old Colony
Sound Labs, Audio Amateur, Box 243,
Peterborough, NH 03458, sells both
Cramolin cleaner and preservative
for $9.95 (there are other
sources). I would clean and
protect the board edge contact of
any ZX80/1 sent to me with return
postage and $2.00.
Ron Miller, 3488 Douglas Drive,
Murraysville, PA, 15668
We have received notice of these
users 's groups since last month.
To check for a group in your area,
call or drop us a note with a SASE.
If you belong to or want to start a
ZX80/81 users' group, let us know
and we'll pass it on.--AZ
Los Angeles, CA: George Kuby ,
213/550-5035 after noon or P.O. Box
34545, Los Angeles, CA, 90034.
San Francisco/San Jose, CA: Paul
Perrault, Stanford Telecommunica-
tions Inc. , 1195 Bordeaux Dr. ,
Sunnyvale, CA 94086, 408/734-5300
Seattle/Tacoma/Everett , WA: Dan
Gallery, 1619 E. John St., #414,
Seattle, WA 98112, 206/325-8186.
Denver, CO: Cap Hamilton, 767 S.
Gaylord St., Denver, CO 80209,
Fort Wayne, IN: Sinclair Midwest
Users' Group, Robert Carroll, P.O.
Box 13042, Fort Wayne, IN 46866.
Lynchburg, VA: Lynchburg Microcom-
puters Users Group, Lane Lester,
804/237-5961 Div. of Natural
Central Pennsylvania: Bill
Russell, RD 1 Box 539, Centre Hall,
PA 16828, 814/364-1325.
New York, NY: ZX Users' Group of
New York, Box 560 Wall St., New
York, NY 10005.
COMPUTER CHESS — JUST $24.95
ZX81 CHESS: a challenging game written
in superfast machine code for the
SINCLAIR ZX81 (req . 16K rampak)
Improve your game: Choose from six levels of play, novice to expert. The
ZX8 1 gives a graphic display of board position and keeps separate records of
your moves and the computer's. Make any legal move, including Castling
and Enpassant; illegal moves not accepted.
Refine your strategy: Set up board to any configuration, even change sides
midgame. Elect "Random Mode" — computer won't always make the same
move in identical situations. Another bonus: a chess clock that records and
displays time per move.
To purchase your ZX81 CHESS package, send check or money order
(postpaid, but add sales tax in Mass.) to: >g\
70 Boston Post Road
Wayland, MA 01778
4K/8K ROM Switch
Marex Electronics, 2805
Abbeyville Rd. , Valley
City, OH 44280
basic kit, $24.95,
assembled, $30.95; full-
feature kit, $34.95,
The Marex ROM switch lets you
use both your 4K and 8K ROMs on a
ZX80 (a 4K ROM won't work on a
ZX81) . The basic kit comes with a
3" square PC board with plated-
through holes, sockets and compon-
ents, plus spacers and screws to
put the case back together with the
PC board inside. An extra $10 gets
you the full- feature kit, which
also gives cassette-load automatic
gain control, a keyboard beeper and
a reset-upon-ROM- switch so you
don't have to pull the plug every
time you switch ROMs. For kit
assembly, you need wire cutters, a
soldering iron, small screwdriver
and pliers, drill and pen knife.
I put together the basic kit.
It came with step-by-step direc-
tions, parts list, schematic and
board layout drawing showing where
everything goes. All the parts
arrived, including about a foot of
solder. Although not a hardware
person, I had no trouble soldering
the components to the board and
plugging it into the computer.
But I did have trouble getting
it to work. First, the directions,
though very clear and simple, don't
tell you how to avoid zapping your
ROMs with static electricity. Not
a big problem here at SYNTAX, where
ROMs abound, but if you have only
2, it could be tough. Then we
found a short between 2 ROM pins on
the PC board. Rex Rickly of Marex
tells us he caught this fault in
one other board, and no one else
has gotten one. It seems that some
plated holes are too large, so the
traces sometimes run too close,
Rex sent an assembled, tested
board, and it works quite nicely.
One of our ZX80s , which always
resets slowly (several seconds with
IK RAM) , would not work with the
ROM switch board. But this machine
only works marginally as it is.
If your luck runs better than
mine and you get a good board, keep
these things in mind: ground your-
self when handling ROMs . When
removing a ROM from the ZX80 , touch
the modulator (silver box in the
rear) . When you plug the ROMs into
the new board, push them all the
way in (till the pins pop into
place) to make good .contact . Yet
be careful not to bend the pins--
they might snap. Three capacitors
on the ZX80 board will get in the
way--bend these down carefully
until the ROM socket pins can plug
into the socket on the ZX80 board.
With these precautions and a good
PC board, you'll be able to use
either ROM without removing one
each time, risking broken pins.--AZ
THE FLAGS REGISTER
(This is part 3 of 12 short pieces
on machine code programming on the
The Flags register, F, is the
other half of the Accumulator pair,
AF. The Accumulator (or A regis-
ter) is where the results of
operations (like add and subtract)
are stored. The Flags register
tells you something about the value
in the A register. AF is just like
the other register pairs HL, BC,
DE, etc. , except that the AF pair
changes with each manipulation; all
of the others change only when
specifically instructed to do so.
Instead of values for each bit
position, the Flags register holds
information for testing. Each bit
stands for a different condition
and can be either or 1 (0=flag
not set, l=flag set). Each bit
represents the information:
H - P/0 N C
128 64 32 16 8 4 2 1
Bit 7--S sign (0 if +, 1 if -)
6--Z zero (0 if result of oper-
ation WAS NOT 0, 1 if result
4--H half carry (used intern-
ally, not testable)
2--P/0 parity/overflow (parity
1--N add or subtract (used
internally, not testable)
0--C carry (1 is a carry from
Most nonprofessional machine
code programmers need thoroughly
understand only the Z flag. The
others can be studied when neces-
sary. For instance, if you have an
address in REM for data (<128; + or
- value) , you can load A with that
value, test bit 7 (the Z flag) to
see if it is positive or negative,
then continue depending on what is
in the Z bit.
Here's what happens: when bit
7 is tested, the Z flag will show
if the bit is 1 (negative value) or
1 if the bit is (positive value) .
It sounds confusing, but just
remember in the Z flag means
negative; 1 means positive. If the
next instruction is JR Z (jump
relative to Z) , then the computer
will jump if Z=l (similar to
IF... THEN GOTO in BASIC). If Z=0 ,
the computer just goes to the next
The Z80 offers thousands of
possible bit- test /test-and-branch
combinations ... try a few.
Next: LOADING REGISTERS WITH DATA
Jon Bobst, Zeta Software, PO Box
3522, Greenville, SC, 29608-3522
Software of the Month Club
Get the most from your ZX81 with 16K, use it to
its full potential, while building an impressive in-
ventory of software. Receive twelve listed programs-
one a month. Programs like Income Tax Recording,
Auto Maintenance, Household Expenses, Price of
Gold Forecasting, Diet Planning, Scrooge's Christmas
Gift and Card List and many, many more for the
incredibly low price of just $19.95 per year. Save
your valuable time and get down to basics!
Make checks payable to BANI-TECH
P.O. Box 1568
Princeton, N.J. 08540
D My check for $19.95 is enclosed.
Please charge my D Mastercard D Visa
Account Number .
24 HR HOTUNE - tt»S«S*t3M
IN OHIO -•0*582-1**.
Ask for operator No. J83
12 monthly issues- 6 bwnontMy
cassettes containing at least 6 ptopamfMefc
ILL Residents add $2.07 tax
3m West lake Street » . ^ ia » , ML, W«1
Rd. , Way Ian
CC $39.95 US
8K/16K, ZX81 only
-Video Software Ltd.
ds, UK DY7 6EQ
e Co. , 70 Bos ton Post
d, MA 01778 (written by
cks , London)
Electronic spread sheets (like
Visi-Calc) let you analyze or model
business and financial problems
quickly and easily. You can try
changes, make corrections, and play
with alternatives. Any task using
rows/columns of numbers you can
carry out with these two programs.
Computacalc and Video-Plan run
on ZX81s with 16K RAM. Neither
runs on upgraded ZX80s . Both are
written in BASIC, run slowly, can
be LISTed, work with ZX printers,
have mostly OK input error trapping
and recovery, left- justify entries
(decimal points do not line up) ,
and let you force recomputation.
Neither program lets you move
rows or columns automatically, nor
can you insert rows or columns. As
a user, I miss these functions. As
a rotten typist, I also miss the
ability to edit complex formulas.
Each program emphasizes a
different approach to analysis--CC
is cell-oriented, V-P is column-
Documentation for each program
is poor. The notion persists among
software suppliers that one manual
can serve to sell, instruct, exem-
plify, explain, and catalog. Once
you learn to use the program, you
will find looking through the
examples just to find a command
annoying. Of the two, V-P did the
CC's manual fits in the
cassette case--4 1/2 columns of
type set 13 lines to the inch. You
get an example that demonstrates
most commands, a list of options to
respond to the major prompt, and
two hints to modify the program.
V-P uses larger type and
provides a 19-page booklet that
covers similar topics. Three pages
describe suggested applications,
and three are devoted to titles and
contents. Each menu option is
fully described by telling the
consequences of each permissible
response. Chapter 5 on functions
lacks clarity and does not explain
which columns may have subtotals.
In most cases the effect of
erroneous entries is explained.
Both programs can behave badly
without warning the .user, though CC
exhibited fewer of these problems.
Any long tape can load with a few
errors which may cause the program
to crash after a while. That's a
needless annoyance- -run the
Syntactic Sum of these programs
when you first get them and at
every load thereafter.
V-P exhibited defects so
serious that I must rate it
unacceptable until they are cleared
up. You can print a table with
data and titles misaligned; sub-
totals can be arithmetically
incorrect; and you can confuse the
program so that the spread sheet
calculates subtotals at intervals
other than those you asked it to.
All of these occur without warning.
CC can give the usual least-
signicant- digit error between row
and column totals, resulting from
Both programs provide huge
grids, much to their detriment.
Neither gives you any direct con-
trol over grid size, and both
calculate the whole grid every
time. V-P took about 10 minutes to
retotal the sheet after changes--
most annoying. CC is much faster
when you use small portions of the
sheet since it only calculates
formulas you put in, whereas V-P
always does all row functions and
column totals--nice, but slow.
V-P only allows functions
between columns, but displays the
function below the column at all
times. In CC, you define cell
relationships freely, but you'll
never see them again unless you
write them down. The function
labels just serially number the
formulas you put in.
V-P handles titles separately
from data, so they don't scroll off
the screen, but V-P doesn't move
the row titles and data together as
it does the column labels. CC
treats the labels as data, and
scrolls them off screen on large
grids. Neither program provides a
title lock, nor does either let you
adjust the row title size
independent of the data block.
Despite the shortcomings , I am
delighted to see programs of this
type becoming available for the
ZX81. Computacalc is a usable
program and both are recommended
for programmers who want to see how
to do these functions in BASIC. --K0
YOU THE POWER!
! KOPAKS'M Touch-A-Matlc gives you
KOPAKTM is now offering The Source*
\ the power lo type more accurately and
'America's Information Utility'. The
! much taster. No wires, no soldering.
Source* gives you the power to access
simple to install . Our unique vinyl over-
a wide array ol services including:
1 lay guides your lingers to the correct
• Barter • Shopping • Business Infor-
i keys Touch typing now possible with
mation • Career Network • Electronic j
your Sinclair* or MicroAce*!
Mail • Medical Advice • UPI News
Service and much more. A modem is i
required to use The Source*.
The KOPAKTM Sinclair* female Con-
Source ID S100.
nector gives you the power to use the
1 Z -80 bus. Edgecard connectors specif-
More POWER on the way! KOPAK'STM
ically made for Sinclair* computers.
| • 46 Pins, 23/23* All pins are gold
The KOPAKTM RS-232 Interlace
| plated • polarizing pin lor correct
The KOPAKTM Bus
alignment everySme! Available with
The KOPAMATICTM Keyboard
Solder-Tail. Wire-Rap and PCBoard.
The KOPAKTM Printer
KOPAKTM Memory Products 1
The KOPAKTM Disc
KOPAK has Nil POWER to Mhwt'
© 1982 KOPAK Creations Inc j
KOPAK Creations Inc.
TM Trademark ot KOPAK Creations Inc
Sinclair* is a trademark ot Sinclair*
! 448 Wis 1 55th Strut
Nil York NT 10019
MicroAce" is a trademark ol MicroAce*
! (212) 757-8698
8K FLASHING PROMPTS SUBROUTINE
To avoid screen flicker, I
came up with this subroutine (at
200 in this example) . The example
program gives 6 flashing prompts.
To change the number of flashes ,
change 6 in line 145. For differ-
ent periods between flashes , change
3 in line 215. Run in SLOW mode.
Rois Harder, N. Van, B.C., Canada
100 PRINT RT 21,6; "C0 TO ID"
10S PRINT RT 21,0; "INPUT"
110 LET P=0
115 GOSUB 200
120 PRINT RT 21,0; "1
125 GOSUB 200
130 PRINT RT 21,0; "INPUT"
135 GOSUB 200
14-0 LET P=P + 1
14-5 IF P=6 THEN GOTO 155
150 GOTO 120
155 INPUT R$
200 LET T=0
205 LET T=T+1
210 IF T=3 THEN RETURN
215 GOTO 205
SYNTRCTIC SUH: 19157, BK
RKe-16 Expanded Memory - 16K 79.95
RKL-32 Expanded Memory - 32 K 149.95
RKL-J1' Single Joystick System 69.95
RKL-J2'Dual Joystick System 89.95
30-Day Money Rack Guarantee
fully Assembled and lesled
• Includes Demonstration Program
32/C Memory plus
Single Joystick System
32/C Memory plus
Dual Joystick System
Include A SG/shfpngi liaixlling
Check or money orda
h-ominstei MA 01453
CURING 16K RAM RANDOM DUMPING
My 16K RAM pack tended to dump
its memory if my ZX81 was moved,
wiggled, or tapped, or if the RAM
pack was squeezed. Sometimes it
dumped for no apparent reason. I
suspected the problem was caused by
dirty contacts at the edge connec-
tor, but cleaning the contacts had
no effect. The cause was mechani-
cal instability in the RAM pack
itself. The problem took only five
minutes to fix, and now my ZX81
with 16K attached can withstand any
amount of wiggling, shaking or
thumping without a memory dump.
This procedure worked for me:
• Open the RAM pack case by remov-
ing the 4 screws and pulling the
halves apart gently. Inside are 2
boards hinged together at the top
by a ribbon cable, book-fashion.
• Inside the front and rear halves
of the case you'll find large tan-
colored cardboard insulators. With
a pair of scissors, trim the
Machine Language Program-
ming Made Simple for Your
Sinclair ZX80 and ZX81
Melbourne House Publishers
$19.95, 160 pgs, paperback
I wanted to review this book
because I'm the person it was
written for. The ZX80 and ZX81
have been my only computers. I
taught myself BASIC and can now do
most of the things I want to with
it. I felt that machine language
(ML) would be a good addition to
speed up some programs and improve
display. The idea of ML "made
simple" appealed to me.
This quality spiral-bound
volume starts on a very elementary
level, explaining how the computer
counts and stores numbers. It goes
through the various registers for
both the ZX80 and ZX81. You learn
to manipulate the registers and
keep track of them.
Each ML command is explained
with exercises as learning aids.
At the end two fine indexes list
the Z80 commands both by number and
alphabetically by mnemonic code.
All instructions are in hexidecimal
notches in the insulators so they
just clear the screw posts.
• On a lower corner of the front
board (the one with the blue plug
attached) you will note 2 grounding
springs that are designed to make
contact with the metallized coating
of the case when it is assembled.
Inspect this area of the board to
see if the pins running from the
blue plug project far enough above
the rear of the board to make
contact with the grounding springs
when they are flexed. If this
appears possible, nip off the
projecting pin ends as close as
possible to the surface of the
board and cover them with a piece
of vinyl electrical tape.
• On the boards in my unit, only 2
of the electrolytic capacitor cans
numbers, not decimal. Most
articles I've seen are in decimals.
Being uninitiated to ML, my
main problem was: what do you do
with it? I felt like I learned all
the skills of woodworking but not
to build anything. A program com-
bining BASIC and ML is included at
the end, but I found it hard to
follow and felt it lacked suffici-
ent explanation to make it useful.
Don't order this book for
quick ML routines to plug into your
programs. Instead, you'll find a
book that seems to give a good
background in ML to help you under- •
stand and build on further informa-
tion found in other articles.
Michael Roberts, Des Moines, IA
This book doesn' t offer immediate
applications, but it's the best
explanation of ML for ML beginners
I've seen. Its friendly style is
painless reading and simple analo-
gies help make this language clear.
This introduction is a must before
moving to books like Zak's Program-
ming the Z80. From from Gladstone
Electronics, 901 Fuhrmann Blvd.,
Buffalo, NY, 14203, or 1736 Avenue
Rd. , Toronto, Ontario, M5M 3Y7.--AZ
had vinyl electrical tape on top of
the cans to prevent shorting to the
opposing board when the boards were
folded together. Place vinyl tape
on top of ALL the cans , and as an
extra precaution stick a strip of
tape on the bottom surface of the
• Reassemble the RAM pack, making
sure that the lower grounding
spring on the front board makes
contact with the metallized coating
on the inside of the of rear half
of the case. If necessary, bend it
gently to insure that it makes
proper contact. The side grounding
spring will be pinched between the
two halves of the case when it is
Burt Haberman, Tuscon, AZ
Reach 19,000 ZX80 and ZX81 users
for $2. 75/ line, 4- line min. Send
ad, typed 35 char/ line, with check/
credit card no. by 15th of month
for next month's issue to SYNTAX,
RD 2 Box 457, Harvard, MA 01451.
Coming soon - ZX81 Monopoly
16K RAM-up to 6 players-imported
from the UK. British board version
family game. Savage PO Box 2681
Kirkland, Washington. 98033
7 IK ZX81 GAMES ON CASSETTE- -$ 10 . 00
Mastermind, Slot Machine, Craps,
Sub Rescue, White Hot Number, and
more. NEW ENGLAND SOFTWARE , Box 691,
Hyannis, MA 02601. (Also for ZX80)
Get loaded every time on ZX-80/81
with LED monitor. Plans $1; Kit
$6+ $1 ship. Play basketball (2
sep. games avail.) in 4K/1K &
8K/2K, $1.50 per list. Send money
+ SASE to: R&H Enterprises, 1408 N.
4th Ave. E., Newcon, IA 50208
Available from SYNTAX . . .
For computing beginners —
Crash Course in Microcomputers $17.50
Covers hardware, machine language and
applications. Reviewed in SYNTAX, Oct. 1981.
Add $1.50 shipping.
ZX80 Pocket Book $14.95
Includes ZX81 supplement. Covers Sinclair
BASIC, data and program listings.
Add $1.50 postage.
For advanced hardware/so/tware users —
Zilog's Z80-Z80A CPU
Technical Manual $7.50
Zilog's Assembly Language
Programming Manual $15.00
Add 5% for shipping.
4K ROM Listing with Sinclair's Original
Designer's Annotations $40.00
Original listing plus utility programs.
SYNTAX back issues available, $4 each.
Call or write for our group subscription discounts.
SYNTAX • RD 2 Box 457 • Harvard, MA 01451
617 / 456-3661
SIMULATED LEARNING for your ZX81/0!
Think of animal; computer tries to
guess it. Computer learns from mis-
takes for next time. List, instr.,
cassette (good stuff! 8/16K)$12 . 50.
Foreign add US$3. SMUG PROJECT, PO
Box 13042, Fort Wayne, IN 46866
FOR SALE :ZX- 81.16K RAM, Radio Shack
Minnisette recorder, cables .manuals
$225.00. Also ZX-80.8K ROM, cables,
manuals, $100.00. Send cashiers ck
or M.O. : V. R. Haupin, Hydrostorage ,
Confederate Dr, Franklin TN 37064.
OFFICIAL SHOW GUIDE for 2nd ZX
Microfair held Jan. 30 1982--46
pages, listing all major suppliers
of ZX81 software and peripherals--
ANIMATED GRAPHICS SUBROUTINE--very
clear, well written primer on how
to do graphics on the ZX81.
Includes demo program, listings and
subroutines-- $2. 95 each. Send
check or m.o. to Mindware Co. , 70
Boston Post Rd. , Wayland, MA 01778
WANTED: ZX-80, 8K ROM, IK RAM and
all paraphernalia that came with
the machine upon original purchase,
especially programmers manual.
State sales offer in writing,
including telephone number, and
mail to: Michael Wido
2922 Kendale, Apt. 142
Dallas, TX 75220
BANTA SOFTWARE now offers Football,
Murder in the RAM, Casino, & our ori-
ginal-Super Monzxer- taped for $3.95
each. Also, we will write programs to
your specs for reasonable $$. BANTA
SOFTWARE, RD #7 , Bethlehem, PA 18015
TAX RETURN HELPER: A set of ZX81
(16K RAM) programs let you easily
enter/examine/modify the forms and
immediately compute the results of
any change. You can also save the
data for future use. Form 1040 and
Sched A,B,C $10 (tax deductible).
Same plus Sched D,E $14. KSOFT, 845
Wellner, Naperville, IL 60540.
Coming Soon - CP Productions. We
will have everything from Adventure
Games to Chess, Cooking, to SAT
Vocabulary and Space Games to
Checking Account Balancing. Send
for a free list of coming programs.
CP Productions, P.O. Box 247, Big
Horn, Wyoming, 82833.
ZX81/16K OUICK CUBE- -guaranteed to
solve any 7 Rubik's Cube (TM) or_
triple your money back. Cube is
set up by entering 54 color faces
of cube. Cube is then solved via
150-200 rotations. Pause control
available at each cube rotation
display. Very interesting program.
Also available for TRS-80 (TM)
I/III, 16K, Level II BASIC. Send
$19.95 for either program, plus
$1.50 postage and handling, to
Alpha Queue Systems, Dept. D, P.O.
Box 20885, Dallas, Texas 75220.
Texas residents add 5% ($1) state
sales tax. Remit checks or money
orders only please. TM- -registered
trademarks of Ideal Toy Company and
"Coin Collection"Mass data storage.
Menu: add/ delete, check inventory,
change cost/value, total cost/value,
search, self running/ saving & more.
(Listable)8K R0M/16K RAM. Tape+Inst .
$9. 95+$l. 05P/H. Programs custom/made
Send a SASE with descript ., example,
and title for free est. M.C.Hoffman
542 Clinton Rd, Paramus , N.J. 07652
16K GAMES FOR THE ZX81/ZX80 8K ROM
ZX8 TREK - 5 levels of difficulty
with 20 battle command options.
CRIBBAGE - the computer challenges
you at the game of Cribbage.
TANK BATTLE - find the computer's
tank before it locates yours.
Cassette + manual - $14.95 ea. game
A.Nisbet, 6 Moffat Court, Rexdale,
Ontario, Canada, M9V 4E1.
#6116 2K x 8 150 NS Static Ram Chip
Available for delivery @ $19.00
plus $1.00 for shipping. Send
check or MO to: Support Systems
One, PO Box 1794, Phila. , PA 19105
MAGIC SQUARE. World's Most Magic!! J
16x16 More Magic thn BEN FRANKLIN' s
Probe with ZX. $2.00 EZRA GROUP II
Box 5222 San Diego, California 92105
LATEST SOFTWARE FOR ZX81 - Games,
practical, math and more! Lowest
Prices Anywhere! Also, Loading
Filter plus other accessories.
Write for FREE catalog to:
GREAT LAKES SOFTWARE, 201 Burlington
Road, Valparaiso, IN 46383
OUR POLICY ON CONTRIBUTED MATERIAL
SYNTAX ZX80 invites you 10 express opinions related to the ZX80 and the
newsletter. We will print, as space allows, letters discussing items of general interest.
Of course, we reserve the right to edit letters to a suitable length and to refuse
publication of any material.
We welcome program listings for all levels of expertise. Programs can be for
any fun or useful purpose. We will test run each one before publishing it, but we
will not debug programs; please send only workable listings.
In return for your listing, we will pay you a token fee of S2.00 per program we
use. This payment gives us the nonexclusive right to use that program in any form,
world-wide. This means you can still use it, sell it, or give it away, and so can we.
We will consider submissions of news and hardware or software reviews. Please
keep articles short (35<WOO words). Again, we reserve the right to edit accepted
articles to a suitable length. We will pay 7 cents per 6 characters, including spaces
and punctuation, for accepted articles.
When you send in programs for possible publication in SYNTAX, please
include the following information:
• How to operate the program, including what to input if it does not contain
• Whether you can run the program over again and how.
• How to exit the program.
• The Syntactic Sum (using the Syntactic Sum program in the February, 1981,
• Whether it fits in IK or 2K RAM (or I6K when available).
• Whether it uses the 4K or 8K ROM.
We pay for this explanatory text at the same rate as for articles in addition to
payment for the program itself.
If you want us to return your original program listing or article, please include
a self-addressed, stamped envelope. Otherwise, we cannot return submitted material.
****L00KING FOR SOMETHING DIFFERENT
*tO run on your Z81? How about some
*thing that lets you investigate
•'your past lif e , . . . or , f ind out just
"what turns on that special person.
*How? 'Astrology ' --based on ancient
^knowledge about the harmonic quan-
*tazation of energy -Astrology does
''•"work! And now, you can write a pro-
fessional personal horoscope . Check
"mate compatability , analyse person-
alities . Not only locates 9 planets
■'moon, node, houses , but prints out an
"interpretive analysis , -making it a
"great party game. Tape $16.Visa/MC.
'•914-2555521. LS.POB 935, New Paltz,
-NY. 12561. Astrology trainer incll6K
LAND THE SPACE SHUTTLE. Your TV
screen becomes the instrument panel
and windshield of the spacecraft.
The runway appears before you,
giving the effect of a flight simu-
lator. Game has several endings,
each dependent upon your skill.
LAND/ AIR BATTLE. Destroy the enemy
(the computer) before it destroys
you. Fly the aircraft through flak
dropping bombs on target. For ZX81
and slow screen Microace 8K Rom.l6K
Ram. Get both games on one tape for
$6.95. Funware 7119 Santa Fe Ave.
Dallas, Tx. 75223
SYNTAX ZX80 is published
monthly by a wholly-owned
subsidiary of The Harvard Group.
Syntax ZX80, Inc.
RD 2, Box 457, Harvard, MA 01451.
12 issues, $29. Single issue, $4.
Kirtland H. Olson
Ann L. Zevnik
Printed by Joseph E. Marhefka, Jr.
Clinton Offset Printers
Clinton, MA 01510
© Syntax ZX80, Inc., 1981. All
rights reserved. Photocopying
prohibited. ISSN 0273-2696
YES! Please send me 12 issues of SYNTAX for $29.
□ My check for $29 is enclosed.
Make checks payable to:
SYNTAX ZX80, INC.
account number ^
□ Please charge my D MasterCard
□ Diner's Club □ American Express
□ VISA □ Carte Blanche account
. bank number (MC only) .
I own a □ Sinclair ZX80 □ Sinclair ZX81
Telephone orders call
BUFFERED EXPANSION BUSS for ZX80/81
For memory mapped peripherals.
Unlimited applications. Perfect for
experimenting w/ computer hardware.
BARE BOARD AVAILABLE NOW
*fully buffered, w/decoders to open
8K of I/O space. Needs 8 chips.
*4 connector positions to fit . 156"
c/c 44 pins popular circuit cards.
*2 connector positions to fit . 1"
c/c. *Room for wire wrap.
*all components readily available.
*fingers for 16K memory pak.
^complete documentation plus free
plan for I/O port,
-'plated thru holes .. legend. . solder
mask. .gold plated fingers
^provision for 3A voltage regulator
BARE BOARD (w/one connector
to the computer) $30 .
Shipping and handling. .......$ 3.
Calif .residents add $1.95 S.Tax
Allow 4-6 weeks delivery.
To order: specify for ZX80 or
ZX81 and send check to:
COMPUTER CONTINUUM, 301 16th Ave.
San Francisco, CA 94118
Product price/availability subject
to change without notice.
(ZX80 w/8K ROM will require minor
circuit modification) .
Complete kit available next month.
EZRA GROUP II
EZRA GROUP II
The ZX80/81's are making a name
with LOW prices . . .
WE CHALLENGE THE SOFTWARE COMPANIES
TO LOWER THEIR PRICES!
for ZX81/ZX80/8k ROM
IK and 16K RAM versions
Graphics Billboard 1.00
SPINNER T.M. (like Rubik' s) 16K. . 2 . 00
Skew-a- Sketch (like Etch) 1.00
Improved Pause (ZX81) 1.00
Linear Programming Ask.
Self Addressed Stamped Envelope
Gets YOU Our goodies catalog
ALL ORDERS AND CATALOG REQUESTS GET
FREE Galactic Messages PROGRAM.
EZRA GROUP II
EZRA GROUP II
P.O. Box 5222 San Diego, California
TEXT EDITOR: (8KROM/16KRAM)Enter and
edit any text or graphic, list/docmt
$10.w/all updates $20. D.O'connell
1219 W.Russell, San Antonio TX 78201
PUT THAT ZX80/81 TO WORK with SORT.
This great collating tool can count
and file 1000s of items in over 29
categories with just IK! $3 gets
you list & notes to learn/build on.
Tom Woods Box 64 Jefferson.NH 03583
Bolton Road. Harvard. Mass. 01451
Permit No. 8